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Why would all passengers be asked not to eat peanuts when there is one allergic person on board?
In this review of BA British Airways Club World London City flight there is one thing I don't understand:

... it was announced that a passenger onboard had a severe nut allergy, so they asked people not to consume nuts on the flight.

I've never seen this in a restaurant or any other setting. I gather it's usually the responsibility of the person suffering from allergy to avoid what they are allergic to (usually with a legally mandated help, like known allergens listed on the menu).
I understand that having a person have an allergic reaction to nuts (which can get very bad) itself is a risk to the whole flight. What I'm missing is how other people eating nuts may endanger the one person with allergy.
The only thing I can think of is perhaps some loose nuts flying into the allergic person's meal (or, more directly, mouth) in a severe turbulence. Is that it? Is it a normal procedure to ask passengers not to eat nuts when there is an allergic person on board?

As a datapoint for your last question, my last two flights to the US on Delta have both had an announcement that somebody has a severe nut allergy so they won't be serving nuts, though they didn't ask people not to eat nuts they might have brought on board.

"The only thing I can think of is perhaps some loose nuts flying into the allergic person's meal (or, more directly, mouth) in a severe turbulence" Allergies can be triggered a lot easier than the far-fetched scenario you describe, I'd recommend you read up on the topic.

@AEhere I just did and ... wow. 5 milligrams put it in a new perspective for me, I had no idea. Things I learn every day.

Relevant, although consider the source: https://www.peanutsusa.com/industry-info/health-nutrition/186-nuts-on-planes-myths-media-and-facts.html

Yeah, it's not anything like gluten intolerance or any of a variety of IgG allergies that many of us have and don't know because the effects are felt 12-72h later and it,s hard to link the exposure to the effects. Peanuts are an IgE, and a nasty one, which means BLAMMO.  Also, a medical crisis on an intercontinental airplane is a much more serious matter than on land where you can dial 999 or 911.

Most restaurants aren't flying at 35000 feet, and you having an allergic reaction doesn't cost the restaurant tens to hundreds of thousands of dollars like an airplane diversion.

No peanuts? I want to rebook my flight!!!

We have prominently posted signs on every entrance door on our entire University campus. "No peanuts allowed on this campus. Airborne peanut particle allergy"

@TemporalWolf Restaurants are also not in a pressurized cabin where you cannot get away, and also does not maintain a 5% humidity and recirculate the air.

The problem with a severe peanut allergy is that you don't have to eat a peanut to be affected.  With a severe enough allergy, inhaling peanut "dust" can trigger a life-threatening emergency.  In a confined space, any number of events could cause an issue: people dumping peanuts into their hands, dusting their hands off, accidentally sneezing while chewing the peanuts, etc.

It's a combination of recirculated air and extremely low air-humidity (<5%).  This causes airborne allergens to stay in the air indefinitely and circulate through the entire plane.  The main problem is once the allergic reaction starts, you can't get away unless you leave the plane, or put on an oxygen mask.

Peanut allergies can be VERY severe.  In this news article, a passenger simply OPENED a package of peanuts 4 rows ahead when everyone was explicitly warned not to at the start of the flight.  The child's breathing airway closed but was saved by an epipen.

Just to add on: This degree of sensitivity is rare, and not everyone who can have fatal reactions to peanuts is this sensitive.  I say this as someone who has a life-threatening peanut allergy, but (at least so far) has never reacted simply to particulate in the air.  Thus, in case someone reads this and is thinking "huh, that's not how [person they know]'s allergy works" --- reaction types and sensitivities can vary broadly and there's not a lot known yet as to why.  Your best source for knowing how sensitive or reactive a person is, is that person themselves.

@A.Rex Looks like i fell for a myth.  Edited and removed that part

My grandson has a severe peanut allergy.  The Doctor has emphasized that this allergy can be fatal if the kid gets a very small dose of peanut, without very prompt treatment!
The common first aid treatment is an injection commonly administered by an EpiPen (or similar) so the EpiPen must be available on very quick notice 24/7.  What many people don't realize is that although the EpiPen injection is effective, it is a TEMPORARY solution to the acute problem, and that the patient must be transported to the Emergency Room quickly, even after the EpiPen injection.
That is hard to do at 36,000 feet.  It also disrupts everyone's schedule.

I wish your grandson never needs the EpiPen and that the quality of his life is greatly improved by this precaution! I've acknowledged both the danger and the disruption to everyone in the original question. What I'm interested in is the part the kid gets a very small dose of peanut - can you please elaborate a bit on that part, to get the idea how great the danger is for your grandson when other people are served peanuts?

@Pavel A cousin of mine has severe peanut allergies.  One time she was kissed goodnight on the check, but the spot turned bright red.  The person that kissed her did have peanuts at some point that day, and had a small amount of the oils linger.

+1 for "...the EpiPen injection is effective, it is a TEMPORARY solution to the acute problem..." - while most [citation needed] people probably have heard of EpiPens, I don't know if they realize they are not a remedy for the allergic reaction.  So, as I've heard some suggest, the solution is not "Just keep EpiPens on planes and we can eat all the peanuts we want".

I would think that a person would be in more danger from someone who had eaten peanuts in the same seat on a previous flight, than from someone eating peanuts on the same flight 30 rows away. Do airlines do the level of sanitation required to remove trace amounts of peanut oils from cushions and armrests between flights? I think not.

I think this answer is missing the fact that this question is not about airplanes.

Just to add to this answer/address the question of peanuts 30 rows away... What happens when the person with the peanut allergy is seated near the lavatory and anyone else has eaten peanuts and also wants to walk to the lav?  I know it's not likely, but aviation is 100% about risk mitigation, and I'm sure the risk here of allergen cross contamination in this case is greater than zero.  Since the cost of asking people to keep their nuts put away is basically nothing, the question becomes "why wouldn't the airline make such announcements?"

Adding to Nexus_2006 comment above:  The passenger 30 rows away eats the peanuts and then walks to the Lav.  Minor turbulence occurs, and the passenger naturally steadies him/herself by resting his peanut oil laden hands on seatbacks up and down the aisle.  Now the person with the peanut allergy gets up to use the restroom and walks up and down the aisle, using the seatbacks for stability...

@Kevin's answer is the reason this precaution is taken. While there doesn't seem to be any evidence that aerosolized peanut oil/dust can cause a severe reaction (source and other source), people think or are afraid that it can. Mind you, if I had a severe enough allergy that I could die quickly without treatment, I might feel the same way because one time that friend of a friend said...
Point is, since aerosolized peanut stuff in a contained recirculated environment puts people on edge and it's the airline's responsibility to care for you, some may take this precaution. This is specific to airline and not other places due to the fact that the sufferer is trapped in a confined space for a long time, in an air recirculated environment without access to proper medical care. Anywhere else, the sufferer can get out and go to a hospital within short order.
Note that some restaurants (5 Guys in the US comes to mind) are so covered in peanuts that they recommend anyone allergic not even enter their store, they just don't want the liability.

Generally good answer, but the part about recirculated air is a common misconception, not a reality. The entire cabin air is refreshed without outside air roughly every 2-3 minutes and what air is recirculated runs through HEPA filters first.

@reirab Did you mean air is refreshed without outside air or "with"?

@chux Yes, I meant "with." Thanks, good catch. Unfortunately, it's too late to edit the comment.

Peanut allergies are nothing to joke about as they are often severe, with very quick onset - the merest hint of a peanut can within a few moment become a life threatening emergency. Once an airplane is in the air it takes a long time to get down even with emergency priority, and airplanes don't have the advanced medical equipment and staff to keep someone in that condition alive.
That circumstance is easily avoidable, which is why it is pretty standard procedure to ask people to make those announcements, and it's why most airlines have switched to pretzels instead of nuts as in-flight snacks. It's not a regulation, it's a risk reduction strategy.
You don't see that happening in a restaurant because people go to a restaurant to eat - a person going to a restaurant can have no expectation they won't come into contact with food, if they have that bad an allergy they would contact the restaurant beforehand and let them know their needs. Also, your typical restaurant is no more than a few minutes from specialized medical help.

We all understand the severity, and how it is especially inconvenient on a flight, but nobody has answered the root question:  How can a person eating a peanut in another row cause an allergic reaction?  Does chewing with the mouth open produce peanut fumes or a fine dust that is inhaled?  BTW, this question is less specific to aviation than many others that are flagged for being off topic.  It is more of a medical question.

@MichaelHall I have never one encountered a restriction like this outside aviation and came across it in an aviation story, which makes it aviation-related for me. I concur about the root question - the nearest we've got is read up on this in comments.

I think this answer is missing the fact that this question is not about airplanes.

IMHO, it's about airplanes to the extent that it may be asking why the paranoia about peanuts on planes and not in other public spaces--and several answers/comments have pointed to reasons that are, in fact, fairly specific to planes.

@StephenS Well, some of them are specific to planes. Others are misconceptions about planes (especially the bit about recirculated air.) At any rate, it seems a perfectly reasonable question to ask here as a common misconception about aviation is still related to aviation.

To be completely honest, this is an overreaction. Yes, peanut dust can cause problems, but the problem comes much more from contact with contaminated surfaces (e.g. armrests, tray tables, etc.) from passengers on the previous flight than from dust transported through the air. Cleaning your seat environment with an alcohol wipe or similar before taking your seat is going to make a lot more difference than banning someone 15 rows away from eating peanuts in flight.
Contrary to popular belief, airliner air is actually quite clean - significantly more clean than in most buildings. If you don't have a reaction from someone on the other side of your restaurant eating a peanut, then you're not going to have one from someone sitting on the other end of your plane eating peanuts, either. Airliners actually use quite good air filters and around half of the air is not recirculated at all, but rather dumped out the outflow valve and replaced by outside air (from engine bleed or a scoop.) So, the odds of any significant amount of peanut dust from someone in row 30 reaching an allergic person in row 10 are extremely remote. The airflow is spanwise (from aisle to window,) so only someone within a few rows of you is likely to breathe in any peanut dust you may generate.
According to a study published by the National Institutes of Health,

The vast majority of U.S. airliners use high-efficiency particulate air (HEPA) recirculation filters for cabin air, and these filters are highly effective at collection of solid and liquid particulates.

And according Patrick Smith's Ask the Pilot, due to the fresh outside air mixed in, "there's a total changeover of air every two or three minutes." This is significantly faster than you'll get replacement air in a commercial building, let alone your home.
The only reason that actually makes any real sense for banning everyone on the flight from eating peanuts rather than only the people in nearby rows is that it does not reveal who actually has the allergy, so it's not as embarrassing for them and they don't risk glares or potential harassment from other passengers upset about their lack of peanuts.

As far as whether this is common practice, there are indeed several airlines that do this.
For example, Delta's policy:

If you have a customer that has a peanut allergy, please contact Delta Sales Support or Delta Reservations in advance to have the peanut allergy information noted in the customer’s PNR.
When Delta is notified that a customer has a peanut allergy, we’ll refrain from serving peanuts and peanut products onboard the flight. We'll also advise cabin service to board additional non-peanut snacks, which will allow flight attendants to serve these snack items to everyone onboard.
On the day of travel, customers should notify the airport gate agent of the peanut allergy, if they would like to request to pre-board and cleanse the immediate seating area.
Unfortunately, even with all the above precautions, we still can't guarantee that the flight will be completely peanut-free.

For those unfamiliar with the industry jargon, "PNR" is "Passenger Name Record" and is just the airline industry way of referring to your reservation.
Southwest stopped serving peanuts entirely last year. To honor the occasion, they set up a tongue-in-cheek display case of peanut packages at MCO.
American Airlines does not serve peanuts and allows allergic passengers to board early to wipe down their seat environment.
United Airlines does not serve pre-packaged peanuts on their flights.

Surfaces shared by all passengers, and direct contact with other passengers.
The greatest risk is that someone will spread peanut oil from their hands onto a surface the allergy sufferer will likely touch. If the person has a sever enough allergy, then they could have a life-threatening reaction even to trace amounts of oil that has made multiple 'hops' from surface to surface to get where it is now. The oil could travel from the nuts onto someone's hands, then from their hands onto the latch handle of an overhead compartment, and then onto the allergic person's hands.
There are surfaces and objects that are common to all passengers. The lavatory door and appliances are key examples. The allergy sufferer might try to limit their exposure to surfaces like this by wiping them down before touching them, but it's very difficult to do this 100%. You begin to see the problem when you consider the 'multiple hops' could go in an airplane, especially when you consider that one such hop could be a person's clothes. The allergy sufferer might brush against a surface and get the oil on their clothing, then have a reaction ten minutes later when they touch that part of their clothing with their hand. Other passengers might also wipe the peanut oil on their clothing if they forgot to ask for a napkin.
What about the previous flight? Wouldn't these surfaces already be contaminated? It's possible they are contaminated yes, but the primary way peanut oil gets removed from surfaces other than regular cleaning is by many people who don't have the oil on their hands touching the surface. After a person gets peanut oil on a door handle, the next dozen people will each wipe away some of it and dilute it with skin oils when they use the handle, thus eventually making it safe for a peanut-allergic person. This has likely already happened as much as can be hoped for from the previous flight since people don't eat during landing but then go about touching all these surfaces during de-boarding.
The peanut-allergic person's life goal is to not be one of those twelve people who had to touch the peanut oil-ed handle to wipe and dilute the oil back to safe levels. It's a game of managing probabilistic risk VS living life outside of a sealed bubble. With a restaurant, as long as they've picked a place where peanuts aren't on the menu or are rarely on the menu, they can manage this risk without help from others. On a plane, they are crammed in and have to share surfaces with scores of other people. Combine that with peanuts being the in-flight snack that everyone has, and it's a very risky time for them.
Imagine you get on a flight and all the other passengers are humanoid-aliens with green skin. The flight attendant announces that since there are so many of these aliens aboard, they are switching the in-flight snack to their favorite dish: raw poison-ivy plants served as finger-food. The aliens aren't harmed by the poison ivy's oil that causes intense itching rashes and hives on humans, so they are too cavalier, grabbing a poison ivy stalk in their hands and munching down on it, then lazily wiping their hands on the corner of their jacket, then grabbing the seat head rest as they get up to o use the lavatory and touch everything in there too. Do you think you could make it through that flight without getting even a single little spot of poison-ivy rash? Maybe, but it's a harrowing ordeal. And that's just poison ivy. The allergy sufferer won't just get a rash but could die from just a little exposure. Try-reimaging that aliens on a plane scenario but instead of poison ivy they are snacking down on a potent poison like cyanide or ricin.

Interesting indeed - I see how complex it might get. Incidentally, you mention one interesting thing - problem of (lack of) sanitizing the plane between flights. As I understand it, the crew asked passengers not to eat peanuts on that flight. Off course wedon't know whether BA sanitized the plane or at least the critical surfaces. I might ask BA about that later! Another thing is that people are asked not to eat nuts, which goes further than just not serving them. In that case it is hardly the snack everyone has, but it doesn't make your answer less valid.

Anecdotal story:
I was on a commercial flight (Delta?) where they announced very clearly that there was a peanut allergy on board, and that peanuts were not permitted for the duration of the flight.
A family near where we sat opened a pack of Nutty Bars. The fragrance of the peanuts - the smell - was immediately obvious. In about 30 seconds, a woman two rows back signaled the flight attendant that she was having health problems related to the peanuts.  It was quick because airplanes are small and have limited air volume.
The family heard about the problem and quickly ate the nutty bars. Once they were not exposed to the air, and the woman's issues quickly resolved as the air cleared.

"airplanes [] have limited air circulation" citation needed.

As a person who has anaphalactic reactions to bees (swell up, hard to breath, cardiac arrest possible), it is fast, sudden and very dangerous. Within 15-20 min, even with an adrenaline shot, I can be in severe breathing difficulty. In a cabin atmosphere of 8000ft that would be far more uncomfortable and would trigger a full scale emergency to the nearest sutiable aerodrome. To any bystander on the plane, who has not seen a reaction before, it would be terrifying.
We swell up, turn red and white, get huge hives all over our skin, struggle to breath and then and can go into shock or seem semi conscious due to the extreme tiredness caused after the epipen.
There is probably not much chance a flight could continue enroute to a destination if a person had a full scale  anaphalactic reaction. It can be a serious and life threatening medical emergency. Luckily the vast majority of peanut allergies are not this severe. [1]
The reason the airline asks you not to eat them is, the airline has a duty of care to protect the passenger while onboard the aircraft [2], they have a responsibility to not discriminate against that passenger and they have a strong commercial interest to avoid a very expensive and disruptive emergency diversion to an alternate aerodrome.
In addition in most aircraft the fresh to recycled air in a plane is 50-50 percent [3], so a lot of the air and any nut dust could be recirculated from row 1 in first class to row 51 in economy, or someone in row 20 might go to the same toilet to walk past someone in row 37 and expose them via touch, breath or both touching the same surface. Even a cabin crew member may collect the nut packet, then touch a food package that gets passed to the effected person.
It is serious, but yet easily caused and so easily prevented.
[1] https://acaai.org/allergies/types/food-allergies/types-food-allergy/peanut-allergy
[2] https://injury.findlaw.com/torts-and-personal-injuries/in-flight-injuries-on-airplanes.html
[3] https://www.tripsavvy.com/air-quality-during-your-flight-54164

The air is run through HEPA filters before recirculation, so it's extremely unlikely that peanut dust or oils from another row would travel via the recirculation system. You have much more risk of this in most buildings than in an airplane.

As @reirab says, air circulation isn’t the issue most think it is, but apart from that this is a good answer. Welcome to Aviation.SE!


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Is it possible to embed CL, CD, dCLda, etc, into a tensor?
Is it possible to form a tensor (i.e. matrix) such that this tensor applied to the apparent wind vector produces a vector representing the resulting aerodynamic force?

Yes, actually the vector of the nondimensional aerodynamic coefficients is related to the nondimensional forces using a coordinate transformation tensor. Then, this tensor depends on your coordinate system (stability axes, wind axes) which in turn depends on which coordinate system is more convenient for your job. For example
\begin{gather}
\begin{Bmatrix} C_{D_i} \\ C_Y \\ C_L \end{Bmatrix} = \Bigg[ \bar{\bar T^s} \Bigg] \begin{Bmatrix} \overline{F}_x \\ \overline{F}_y \\ \overline{F}_z \end{Bmatrix}
\end{gather}
where $\bar{\bar{T^s}}$ is your stability axes coordinate transformation tensor which incorporates the sines and cosines of the rotation angles and the right hand side vector is the nondimensional force components. For detailed derivations regarding this coordinate systems and their use you may want to check Chapter 6 of the book of Mark Drela, $\textit{Flight Vehicle Aerodynamics}$ from MIT Press.

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Requirements for Steady Level flight at various speeds
Let an aircraft in a steady level flight be trimmed at certain speed. A level and steady flight at a higher speed can be achieved by changing throttle and elevator together ( and not just by changing elevator or throttle alone). How?

http://aviation.stackexchange.com/questions/2980 ?

The question is unclear, but @Federico 's suggestion is likely the answer expected.

From a purely practical standpoint, let's say you're in a Cessna 172 (a common light aircraft often used for training) and you're in economy cruise at 2400 rpm at 6,000 feet on a standard day. According to the cruise performance chart I have here, you would be using 60% power, burning 6.8 gph, and have a true airspeed of 109 kts. You're hand flying the airplane as it has no autopilot.
Now the cute gal that you've talked into taking this trip with you mentions that she's beginning to need a bathroom. You neglected to bring along a urinal (and maybe more than a urinal is needed), so you decide to speed up to the maximum cruise speed for 6,000 feet. You consult the cruise performance chart and see that you can get 75% power at 2600 rpm. That will increase your cruise speed to 120 kts at the cost of burning 8.4 gph.
You would smoothly increase the rpm to 2600. As the power came up, you would have to hold a little forward pressure on the elevator to keep from climbing. If you're used to the airplane, you might unconsciously reach down to the trim wheel and roll in a little down elevator. In any event, you will eventually want to trim out the down elevator force you're holding on the control wheel.
If you set 2600 rpm to start the speed up, you'll notice that the rpm goes a little above 2600 as your speed increases (this is a fixed pitch propeller), so you monitor and adjust the rpm as necessary to settle on 2600 rpm with elevator forces trimmed.
If you have an autopilot with an altitude hold function but that doesn't control the power, all you'll have to do is control the power.
If you have an autopilot with FADEC, just set what you want and it will do all the work from there.

I'm not sure if the question is how or why.
Assume that the throttle is changed (let's say increased) in level flight. The following things happen:

The speed increases.
The increase in speed increases the lift produced by the wing and the aircraft attitude changes (it pitches up) and the aircraft is no longer in level flight.
In order to trim this, the elevator correction has to be applied.

On the other hand, assume that the elevator is used to pitch the aircraft down. Then the following things happen:

The lift (and drag) decreases and the speed increases.
In order to maintain the speed, the engine power has to be reduced.

So, its not possible to maintain level flight at a set speed at a given altitude using only throttle or elevator.
Of course, at different altitudes the aircraft will be trimmed for different power settings for fixed elevator setting.
One way to understand this is that the energy is conserved and if the kinetic energy is changed (by changing the speed), the potential energy (altitude) should also be changed for level flight. Otherwise the aircraft will trim itself at another stable altitude.

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Could an A220-300 swap engine types easily?
For example, could an A220-300 with the PW1521G swap engines to the PW1524G? If yes what obstacles need to be cleared for it to happen?

I think the answer to this question can be greatly improved if OP could say why he needs this information.

I have not been able to expressly confirm this for the PW1500G, but basically all modern FADEC-controlled engines within the same family are designed to be converted between thrust ratings with software changes only, and typically a 'thrust plug' hardware license key.
The PW1521G and 1524G are the same family designed to be fitted to the same aircraft, and therefore probably mechanically identical. Changing the engine type, therefore, wouldn't even require getting out a crane and changing the actual engine.
It's a matter of filing the appropriate paperwork, paying the fees to the engine manufacturer and possibly aircraft manufacturer, plugging in a new thrust plug, and changing settings. A higher thrust engine will degrade more quickly and require more frequent maintenance, and this will result in higher costs. Some airports might also charge higher fees, especially if the MTOW is also raised on paper.
This question has some information, mostly about the 737NG.

What is this "monica" stuff?

@Jpe61 Who or what is Monica and why so much notice from SE users?

Dang, I'm gonna need a more concice version to keep up interest...

As per EASA type certificate (link to pdf) all Pratt & Whitney PW1500G ensiges share a common "Engine Installation and Operating Manual" (PWA-8828).
It would therefore be safe to say that the engines share the same mechanical and electronic connections, and would be interchangeable as such.
The type certificate lists as the only difference between the PW1521G and the PW1524G models the "Data Storage Unit (Ratings Plug)". While not being a specialist in this matter I still would suggest the swap would not be entirely "plug and play", as there may be slight variance in control parameters such that some kind of adjustments might be necessary across the FADEC system.
The question mentiones that the engines on A220-300 are PW1521G. However this pdf document suggests that A220-300 (at the time of the creation of the document the CS300) uses PW1524G variant, and that the PW1521G is used in A220-100 (formerly CS100)

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How are Airlines like WizzAir able to fly between Saudia and Italy
As stated in the title I'm looking to understand how an airline like WizzAir Malta can fly between Milan, Rome, and Vienna from Riyadh. Their AOC is from Malta, and the EU has no open skies agreement with Saudia. So how is this possible?

Don't know if they have separate AOC for Saudi operations, but at least some of their aircraft are in UAE registration (A6)

"Their AOC is from Malta"

Wizz Air Malta Limited has an operator licence from Maltese authority and an EASA AOC (air operator certificate), EASA.AOC.003, since Sept. 2022:

Wizz Air, Europe’s fastest growing and most sustainable airline, is pleased to announce that Wizz Air Malta has been granted an Air Operator’s Certificate (AOC) by the European Union Aviation Safety Agency (EASA) and an Operating Licence (OL) by the Malta Civil Aviation Directorate (CAD).

Malta is part of the European Union, Wizz Air can fly to Saudia like other EU operators, pursuant to a pre-existing Bilateral Air Services Agreement (BASA) replaced by an Air Services Agreement (ASA) after all BASA were overruled by the Court of Justice.
The EASA AOC is listed here.


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Do the Blue Angels use their #7 aircraft for photography during rehearsal flights?
I recently had the privilege of watching the Blue Angels fly their rehearsal for an airshow performance, and I noticed that an additional aircraft would often fly a very loose formation with the aircraft in diamond or arrowhead or echelon formation.  It never seemed to join the formation itself, never trailed smoke, and would break off when the main formation split, but then rejoin later to the same loose trail or overhead observation position.  When the team pitched out for landing, it pitched out last, and on landing it was evident that it was the #7 aircraft, which is a 2-seat jet.
The question is, was this aircraft (and presumably, the back-seater in it) capturing photography of the main formation, either as a debriefing tool or for other purposes?  Is this typical for the rehearsal flights?  And if so, how long has this been the norm?
In any event, thanks, Navy - it was a beautiful show, and the touch of hearing I probably lost to the low pass with full burners, was an entirely worthwhile tradeoff for the goosebumps raised.

Yes, it might have been a photographer in the back seat. Or a local civilian...politician, press, or other VIP. Also, a potential future team member. The USAF Thunderbirds do the same.

The Blues have two specially built F/A-18Fs, #7 and #8 that go along with the team.  They serve a number of functions on the road, including a spare jet should one of F/A-18Es be unavailable for the shows due to maintenance issues, transport for other member of the Blue Angels, media and VIP rides and aerial photography duties.  The USAF Thunderbirds have 2 F-16Ds for a similar purpose as well.


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Can a landing aircraft snag multiple wires when landing on an aircraft carrier?
There are 4 arresting wires on an aircraft carrier separated by about 50 feet and usually the pilot tries to snag the 3rd one but he does have the option to snag the first or second one.
What stops the tailhook from engaging the wires in front of the airfraft as well?   Is it assumed that they will also get engaged and the regulator on each arresting engine is tuned to accept it?

I don't have any military aviation experience, but it looks like once the tail hook snags a cable, it's pulled back and upwards, which would prevent it from snagging a second wire.

I completely agree with  @Johnny. This picture shows pretty well how it works

As a side note - carrier aviators never aim for the first two wires (on a 4-wire ship). The aim is almost always to tag the 3-wire. Tagging the 1-wire is considered dangerous.

what is the purpose of the first wire then?

Now I guess not because this must be a case that the engineers tried hard to avoid. But if you look like the early days of the arresting system it might have actually happened.

@user99379 The deck moves.  while the 3 wire is the preferred trap, a trap beats a bolter.  So if the plane comes in a bit short, catching the 1 wires still makes for a recovery.  The pilot can work on better approach/technique on the next try.

@user3528438: The very first landing (by Eugene Ely, 1911) used a series of sandbags  on each side of the deck with a rope strung across. When the pilot landed he caught each pair of bags as he proceeded down the deck, slowing him more and more.

The answer is quite simple:
1. When touching down the nose is in a pulled up attitude, therefore the tail is farther down then normal. As soon as the airplane touches down (on all wheels), the tail is higher, thus the hook is higher.
You can see how the aircraft is in a nose up attitude, but gear and hook are on the same level. If the aircraft was sitting on all its tires, the hook would actually touch the ground. (This might not even be the case on all aircraft, though!)
2. This is the much more important reason: The hook is pneumatically pushed onto the deck (Google for the "F-14 Tomcat Pilot's Flight Operating Manual Vol. 1, Volume 1". Interestingly Wikipedia (is it a source?) says there are hydraulic and pneumatic hooks) but as soon as the hook hooks to the cable, and pulls on it, that pneumatic pressure is overcome and the vectors of the forces go from where the hook is attached to the plane to where the wire comes out of the ground (and vice versa).
Note: I guess its a combination of both, hydraulic and pneumatic. As hydraulics are not compressible, a valve would be needed to release the pressure built by the yank of the cable. So air pressure (pneumatics) would probably do a better job on keeping the hook down as long as no cable is attached. The retraction of the hook is done hydraulically though, and the way it is written in the F-14 Tomcat Pilot's Flight Operating Manual Vol. 1, Volume 1 it seems like the pneumatic pressure is kept even with the hook retracted...
As you can see here, the hook is actually almost parallel to the deck.
3. Last but not least: There is no space for two wires on one hook. Let's say the airplane would catch the first rope, and for some reason (it should definitely not happen, but let's just pretend it does) the hook is still on the ground where it would hook up to the second wire when crossing it, then it will maybe drag it along for a short time, but it can't really hook on as the hook is made to fit exactly one wire. This can be seen on this picture:

On touchdown the nose is never pulled up, it is held at a constant AoA for the entire approach.  The height of the tailhook is actually longer than the gear when sitting on all tires (the nose up attitude actually lowers the hook height even further), and it cannot be fully extended unless the aircraft is airborne.  Sitting on the tires, the hook is blocked by the deck, and a little warning light illuminates in the cockpit telling the pilot that the hook is not fully extended.  Also, as soon as the hook catches a wire it is yanked parallel (every time) preventing #3 from being an issue.

Okay, thanks for that input will edit accordingly

Thanks so much for the answer.  I don't think I realized that the wires were so close to the deck to begin with.  I imagined them somehow off the ground so that the hook could grab them.   I see that makes no sense now since the aircraft itself would run into it.

great pictures!

The last picture is broken.

@jklingler still works for me...

No, the hook is not capable of catching more than a single wire at a time.  There is a hydraulic dampener in the hook, the snubber, that keeps the hook pressed into the deck during touchdown.  This was designed to help alleviate a phenomenon known as hook skip bolters, when the force of the hook contacting the deck causes the hook to bounce; however, the hydraulic force of the snubber pressure is immediately overcome when the hook catches a wire, and the hook is drawn up almost parallel to the flight deck as the cable arrests the aircraft.

I've been out of the business for a few years now, but I recall that the snubber was pneumatic vs hydraulic.  Because air can compress, while hydraulic fluid does not...


text:
Why does British Airways fly a short haul flight in a B767?
British Airways operate a flight from Edinburgh airport to Heathrow airport every morning in a 767. Aren't these wide-bodies meant for long haul flights?

How far apart are those two locations?

Roughly 310 miles - give or take 30..  @SpongeBob

Aircraft selection for a particular route is quite complex, especially for a large airline that operates many different types of aircraft.  You're correct: generally speaking widebody aircraft are used for longer flights, but there are a number of other factors at play.  Some of these could be that a route has a very high peak demand, where a lot of people want to go from A->B at a given time.  LHR to Edinburgh seems particularly likely to be one of these city pairs.  Sydney to Melbourne is another one, and is only about 400 miles if my memory serves.  In both of these cases there is a dominant national airline in the mix (BA, Qantas) whereas in the USA there are almost always 3 or more large airlines operating any heavy route (New York to Boston, or Washington DC to Chicago, etc).
Aircraft scheduling also plays a role.  For example, the 767 in question might be scheduled to fly from Heathrow to Edinburgh and back in the morning, before picking up a long-haul flight to the USA in the afternoon.  If there's a 4 hour "gap" in the schedule for that particular aircraft, it might make more sense for the airline to run it as a short out-and-back rather than have it sit on the ground at LHR.
Also, Heathrow is notoriously busy, and getting a takeoff/landing slot there is extremely expensive.  The high landing fees are charged at least partially regardless of the size of the aircraft, so there is some economic motivation here to divide those fixed costs by a larger number of passengers.
As another data point, I checked the daily schedule between Haneda (the main domestic airport in Tokyo) and Hiroshima (~400 miles away) and found the following list of flights:  9x 737, 4x 787, 2x 767, 2x 777 - so in this case you have almost half the flights on widebody aircraft, and probably closer to 75% of the total seats.
It's also entirely possible (I haven't checked the schedules) that this 767 run is temporary, due to a period of peak demand or at a point in the year where the demands on that aircraft type are lower elsewhere in the route structure.
So in summary: it's very hard to know all the reasons that a flight might be operated with a specific type.  You need to know a fair bit about the economics of the city pair, the fleet makeup of the airlines, the likely competition for the route, how the route timing interacts with other flights, the congestion level of the airport, and a lot of other things.

As I know b773(cathay), a333 and b744 (air china) are used for between hongkong and taipei, china southern even use a388 for guangzhou to beijing route

The size of the airplane mostly determines how many people it can hold (around 275 passengers for a B767).  If Edinburgh to Heathrow is common route for businessmen and woman who commute often then using a larger plane is more economical for the airline.  Using something such as a Bombardier Q400 which is a common "puddle jumper" airplane might cost less per trip, but it would need to make significantly more trips.
A Q400 holds around 85 passengers, so you would need to make over three trips in a Q400 to transport the number of people who could fit in a single 767.


text:
How realistic is Google Earth Flight Simulator?
Sometimes I like to fly a bit in flight simulator in Google Earth (not the Pro version), and I was wondering how realistic it is. There are two planes you can fly. I included some stuff I personally tried.

F-16

Max altitude (starting from ground): 46200 ft (14081.8 m)
Max altitude (starting from the highest google earth let me start): 80000 ft (24384 m)
Max speed while falling down: 1450 knots (2685.4 km/h)
Max vertical speed: 980 knots (1814.96 km/h)
Flies rather stable, I can do some aggressive maneuvers without any problems. Difficult to land. When I'm very high, it's difficult to get control of the aileron.

SR22

Max altitude (from ground): 19800 ft (6035.04 m)
Max altitude (from highset starting point): 60000+ ft (18288+ m)
Max speed while falling down: 550 knots (1018.6 km/h)
Max vertical speed: 155 knots (287.06 km/h)
Not very powerful. Quite unstable (aileron always moves by itself). Easy to land.

Interestingly, Google Earth allows you to fly beneath the surface of oceans, and it flies exactly the same as in the air. The support for taking off from a real airport is rather limited, but it's there. It supports a full ROM afaik.

It is not "realistic" at all.  For that matter, most PC flight sims aren't.  I can land a Cessna in real life without passengers realizing we even touched down.  I can't even land a Cessa on the runway in a PC flight sim (xPlane 10/FSX)

The fact that there is a difference in maximum altitude depending on whether you start from ground or some point higher suggests that not much. Where you start does not affect at which altitude engines will no longer provide enough thrust to maintain altitude nor at which altitude stall speed exceeds critical mach number and you get in the coffin corner.

"Google Earth allows you to fly beneath the surface of oceans, and it flies exactly the same as in the air." Didn't this already answer your own question?

@Keegan you should give it a try using X-Plane 11 and VR (I use Windows Mixed Reality). It makes all the difference. I was almost immediately flying a perfectly square pattern, and touching down just past the numbers, on center line! It is amazing! I've read that if the head tracking is spot-on that your brain will accept the visual graphics readily. Being able to look around the cockpit, check the correct time to turn base, etc, made all the difference! I even had a memory later of my virtual flight that for a moment, I thought I had actually been up for real, earlier that day!

How realistic is Google Earth Flight Simulator?

It is very unrealistic in most respects.
I believe there are a number of important ways you can measure realism from a pilot's perspective:

view out the windows
appearance of instrument panel
mode of operation of pilot aids like autopilot, autothrottle
flying controls

physical character
responsiveness

interaction with ATC
effects of wind, weather, turbulence, rain, ice
aeronautical characteristics of aircraft

It would be easy to focus solely on the last of these, but from my perspective this is not really the most important.
Here's a few dissimilarities that occur to me.
View
The SR22 doesn't have a HUD.
I'm pretty sure the SR22 cockpit windows would take up a much greater area of my vision than my computer screen does. Especially peripheral vision. Also in a real SR22, there is important stuff to look at below the windows.
Instruments
Do these look alike?

Controls
In Google Earth you don't have anything like the range of controls that have to be used, where are all the switches, knobs and other dohickeys you find in the real SR22?
Waving a mouse around is nothing like moving a control column around. With a control column you have a much different sense of the position of the controls. Moving a mouse involves completely different muscles and different motions.
Moving a throttle lever is completely different to pressing PgUp and PgDn buttons to move a throttle position in increments
Feel
In Google Earth you don't hear any engine, you dont feel any vibration, you don't feel any turbulence, you don't feel anything in an uncoordinated turn or when pulling out of a dive, you don't feel the unevenness of a runway.
It's hard to really feel oriented in a simulator when your sense of balance and peripheral vision tell you you are sitting upright at your desk, not inverted and spinning towards the ground.
Disclaimer
I'm not a pilot, I have sat in the pilot's seat of a small Cessna and manipulated the control-column and rudder to make a few turns and attempt to maintain speed and altitude under the direction of a pilot. I've done the same in a glider, and I have done some take-offs and landings in a fairly amazing full (though static) commercial 737 simulator with full cockpit reproduction (all seats, panels, motorised levers, switches etc that you'd find in a real 737 cockpit, wired to a large rack of computers).
 A more realistic simulator
Google Earth is nothing like any of them in almost any respect.
It's a fun game though.

Maybe you should try "Prepar3D"

This doesn't really add anything that this question doesn't already cover, and it is even more obvious that Google Earth lacks many aspects of a real aircraft.

@fooot I would disagree. This question specifically targets Google Earth, and even compares the SR22 specifically. While it isn't completely original, it definitely adds something.

@evertheylen It's just that your question only really mentions performance, but the answers here mostly cover the view, movement, controls, etc., which are already discussed in the other question (and they apply even though it's about a different simulator). Of course it's your question, so you are the real judge.

My question contains a lot of data because I thought it could be useful. It's more difficult to turn 'how it flies' into objective data though, so that's why there are a lot of measurements in there. But I get your point.

In Google Earth, the airplane has no physical stress limitations except touching the gruond. And I can reach 1600 knots of IAS when diving from 100000 ft using the F-16. Also the SR22 reaches 500 knots of IAS.

So the next question is... what is the most realistic simulator? (That you can run at home)?

@Cloud: You could probably squeeze one of these into your home or garage.

@RedGrittyBrick wow! But for how much $$$ ?

@Cloud Try out FlightGear. It is excellent, especially for being priced at 0 and open-source.

@neverMind9 Ok thanks!

What is great about google earth flight sim is what makes it unrealistic. I can experience things I would never have the opportunity to experience: like diving down the face of Everest at full throttle, Landing at the bottom of the Marianas Trench, skimming just beneath the surface of the water as we approach LA at 1200 knots, and landing on Hadley Delta on the Moon. All for free. All safe, and tell  my friends how I like to land at Boston, Heathrow, and a tiny airport in Peru surrounded by mountains.
The truth is I am terrified of getting on a real plane, but Google Flight simulator's suspension of reality restores the fun of flying, and makes me wonder if I should not be so scared to get on a real plane.

These are all valid points, and I guess it does answer the question in a round-about way, by showing just how unrealistic it is. Also, no, you shouldn't be afraid to get on a real plane, and you probably rationally understand that. However, if we were all rational, there wouldn't be any phobias, and what fun would that be?  :)

Is it realistic... No...
As mentioned in the other answer the first main gaps are the HUD which an SR22 does not have to my knowledge and the flight dynamics which don't seem real. But keep in mind that google most like had a few people make this as a fun little addition to google earth I don't think its intended to be a realistic simulator. I am a pilot and a big fan of simulators as they are a great tool but they are just that, a tool. The flight dynamics in Google Earth are not what they would be in a real plane and I would never expect that. There are lots of issues with home based simulators and realism. There are full moving sims out there for pros but in the home market, unless you are this guy you are only going to get so much realism.

Movement

While the sim has basic pitch up and down, bank and roll functions it does not feel anything like flying a real plane. Your desk chair is not going anywhere.

Flight Dynamics

I have not flown an SR22 yet but I would imagine they dont handle like they do in that sim. There are other simulators out there (X plane) that have the ability to make very real simulations. Your seat will never move but the flight dynamics of the plane are close to the real thing and good for practice.

Control Input

A real plane is not flown with a keyboard... Yet... but if you do have a joystick or yoke you can get somewhat of a feel for real planes. The issue is that your home yoke will not provide the feedback a real plane does (at least a small plane). I fly the Piper Warrior and before trim there is quite a bit of force on the controls, more than the little springs in my yoke provide.

View

Unless you have a bunch of monitors you will never see in a sim what you see in real life. In a real plane you can see all around you, but you need to keep in mind you are playing a game not flying a real plane.

Its a tool

Simulators are great tools, they can provide a great platform to train in and get to know the systems of a plane and how they work. However they will never (at least not now) replace real flying no matter how hard you try. Sim's strive for realism but they are in the end of the day a simulation of a physical experience and nothing more. The Google Earth Sim was clearly put together to be more fun than real. The runway roll was almost non existant and a single click of the up arrow put me in a stall which is clearly not realistic.
If you want to see how close it is, go to your local airport and see if they have a flight school that offers an intro course. You can get behind the controls of a real plane and see for yourself!

I don't expect realism from Google Flight Simulator, but in providing a reasonable simulation of real world scenery I haven't seen anything nearly as good.
Takeoff scenarios aren't always true to typical flying conditions.  Maybe one or two weeks out of a whole year, planes head east to take off at LAX; at all other times they face west, over the beach and out over the ocean as soon as they take off.  But in Flight Simulator you always fly east from LAX.
Google Earth Flightsim works on the Moon and on Mars. Apparently atmospheric conditions are modeled the same as they would be on Earth, since the aircraft seem to behave the same with regard to maximum altitudes and so forth.

"I haven't seen anything nearly as good". With due respect, you have many other PC simulators to try, that are ways better about aerodynamics and visual details.


text:
What is the working principle of g-suits?
Pilots since world wars have been wearing g-suits in fighter planes to minimize the effect of high g encountered by them during close maneuvers.

How do g-suits help in minimizing the effect of high g's on the pilots?
What is the maximum g that a g-suit could handle properly?

How do g-suits help in minimizing the effect of high g's on the pilots?

G-suit create extra external pressure on the limbs (legs in particular) to prevent the blood to stagnate far from the heart. In normal conditions specific biological systems automatically return the blood from the extremities to the heart, but when subjected to high G loads these systems fail, as they are not designed for such conditions.
By creating pressure on the body the G-suit alleviates the G load perceived by the body.

What is the maximum g that a g-suit could handle properly?

The main limitation is not only the amount of Gs, but for how long the human body can sustain them (spoiler alert: not much)

Image source
As you can see the Gs usually experienced in a fighter aircraft (blue line, see diagram on top right) cannot be sustained much beyond 3 seconds if they are of even moderate intensity. The G-suits help the body resist slightly longer.

What's interesting to me here is how the F-16 seat (and less so the F-22) is tilted back to turn some of the Gs experienced in the blue direction into Gs in the more forgiving red direction.

@ToddWilcox please don't get confused by the diagram: to "convert" blue into red you should tilt the seat forward, not backwards.

Blue is positive Gs driving blood towards the feet, right? Wouldn't that make red indicate Gs driving blood towards the back/spine (eyeballs in)?

@ToddWilcox blue (up) drives the blood down, I then understand that red (back) would drive the blood in front.

That does make sense in terms of the diagram, but not in terms of actual G tolerances of humans. Hmmm...

@ToddWilcox I agree with you, but I cannot find a better diagram. If you can, I will update my answer.

Isn't that diagram missing the forward-acceleration line?  Also, why does the acceleration tolerance drop off dramatically for very brief exposures?

@Sean yes, it is missing, I could not find one with that included. For the why part, I think you better ask on biology or health, I cannot answer that.

Additionally to what @Federico wrote, g-suits press the legs by using inflatable sacs sewed in the suit. The suit is connected to a valve on the aircraft (or spaceship). When g forces increase, the valve pushes more air to the sacs and inflates them.
As for the limit, I think it is 9 g's but I don't have any citations. Also bear in mind that g limit has to do with other parameters as well, such as cockpit and seat design like HAC (high acceleration cockpit).

More primitive suits use liquid or gel; as Gs increase, the gel is forced downwards toward the legs. It's also interesting to note that they can't always be used; the inflation of the leg cuffs in the G-suit can restrict movement of a center stick, so the Blue Angels famously do not wear them, and "graduation day" involves staying awake through a max-G 360 turn. The Thunderbirds do use them, as the F-16 has a side stick.


text:
Are parked airliners always connected to a ground power unit?
I'm wondering if commercial passenger planes, like the A320, are always connected to the ground power unit (GPU) when they are at the gate? Even if for a quick turnaround.

Being connected to ground power is the usual case, but there are exceptions.  Typically, the most common reason to not be connected is if the ground power unit at the gate isn't working.  (Because aircraft use 400HZ AC current at some fairly high amperage, you can't just plug in directly to the standard electrical mains -- a dedicated Ground Power Unit is required, which incorporates some safety features so that equipment isn't damaged even if the unit is unexpectedly disconnected.)
Other reasons could be in the case of a quick turn, the pilots signal to the ground crew not to bother.  Also, if high winds prevent the ground crew from connecting the large yellow air conditioning hoses to the aircraft, then the jet's APU will be running anyway to provide air conditioning, so there's no great need to connect & later disconnect the ground power... the pilots just let the APU power the electrical system as well at this point, saving the ground crew a couple of steps & a couple of minutes.
All of this is less common than the alternative case, though, where the ground power and ground air are connected and the APU is shut off.  The air & electricity from the gate are cheaper than running the APU to provide those, so most often we prefer to turn off the APU until we get close to time to push back.

Any reason aircarfts use 400HZ AC current, rather than the standard one?

Good question -- see here


text:
Why the use of twin tails?
On a number of aircraft such as the:
Antonov 225:

A10:

F35:

Use twin tail designs. I understand for military aircraft that the benefit is it allows for a small tail cross section. Reducing the chance of it being damaged in combat.
In the case of the A225 and other similarly designed cargo aircraft it means the rear of the aircraft can be more easily designed as a cargo hatch.
Are there any other reasons why a twin tail design is preferable over a single tail design?

A225 is a special case, as it was first designed to carry the Buran shuttle. There was the same problem as in the Nasa shuttle carrier, the piggybacked shuttle creates turbulent air behind it. So the vertical surfaces are moved away for the center to prevent flutter. But you may imagine the reason for the other design with a central engine.

related, but exactly not a dupe.

Possible duplicate of http://aviation.stackexchange.com/questions/24020/what-are-the-advantages-of-single-vertical-stabilizer-over-a-twin-set/24026

This constructive solution can be dictated by a number of reasons:
Aerodynamics - for AN 225, 747 Shuttle Carrier Aircraft, A-10 (control surfaces are more effective outside turbulent air);
Some sort of redundancy - for military airplanes F-35, A-10;
Easier construction - since the surface being smaller aerodynamic loads are smaller the structure can be lighter wight;
Radar cross section - F-35, SR-71;
Stability considerations: the arm for the vertical surfaces is a little longer than the arm of a potentially single surface on the longitudinal axis of the aircraft, so the two vertical surfaces combined can have a less surface area than a potentially single surface.


text:
What is the equivalent height of a parachute landing?
I understand that this will vary depending upon the equipment used, the bodyweight of the jumper, barometric pressure etc, but what is the approximate equivalent height of landing from a parachute jump? I have heard people say the impact is equal to jumping from 6 feet up onto the ground - and yet I have seen members of the Red Devils land seemingly as easily as stepping off a kerb.
(Mods: I have seen this question which is why I ask here, please relocate to the appropriate SE if off-topic)

Surely depends on your horizontal speed too.

Don't forget then those most likely to use the classic round chute these days (paratroopers), are usually carrying gear -- up to 150 pounds worth.  Load up and then jump from 6 feet; it makes a difference.

Can't you stop almost all your velocity with a correctly executed flaring? Most modern parachutes allow you to control your lift. Do it too early and you'll stall. Do it at the right moment and you touch the ground gently.

As you have intimated in the question, how hard you hit the ground is very dependent on a number of factors.
When I did my training to jump using a classical tethered round chute we practiced landing from a platform of about 5 feet, so six is perhaps a hard landing. That's, roughly, hitting the ground at 12mph.
Folks like the Red Devils typically use an parafoil chute. Basically a self inflating wing. These can be steered and pitched upward to bring the trooper to a stall or even go up if they have enough forward velocity. So yes, you will often see them stop in mid-air and step down. This means this type of parachute has NO equivalent jump height. In fact if flown incorrectly you can crash into the ground at serious speeds.

Regular "military style" parachutes provide no control over lift and only minor control over direction. With these your descent rate is totally dependent on size, weight and air quality.

Interestingly, with a regular chute, what makes landings "harder" is not so much the effective height but the amount of horizontal velocity.
You are trained to drop and roll when you hit the ground to absorb the impact.

This works great if you have any horizontal velocity to help you initiate the roll. If however you are coming straight down it's not so easy.. and your knees end up in your chest...  as I found out the one and only time I jumped out of an aging Cessna.  Too much horizontal velocity and that roll gets rather violent.

There is probably no equivalent, since there's a fundamental difference: when hitting the ground descending with a parachute, you are moving at a constant speed, with zero acceleration, but when you hit the ground after jumping from a given height, you're moving at a speed that increases with time, since your acceleration with respect to the ground is not zero, but 9,8 m/s/s

I think that "equivalent height" is defined based on speed and acceleration is neglected, i.e. "you hit the ground with the same speed you would have if you were jumping from an height of X"

@Federico When you hit the ground after jumping from a given height, you first touch the ground with your feet, that stop moving at once, but, at that moment, your chest, arms and head, to cite the most distant anatomical structures, are still increasing their speed. As a consequence, the landing sensation is different. In my experience, landing with a parachute is different, very different, from landing after jumping from a given height. I think that most people having experience with parachute jumping will believe the same...

In that case equivalent jump from which height of a train going at which speed?

@Vladimir When descending with a parachute, you do always have a horizontal velocity component (that may be zero, if it's a calm day). Vertical and horizontal velocities add up as vectors, and the resulting speed may be quite high...

I didn't say anything against that, did I?

authors: Vladimir F Героям слава


text:
Is IWA (Phoenix Gateway) a Federal Contract Tower?
how can I find out which airports are operated by the FAA and which are FAA-contract (or even independently operated)? I'm currently looking specifically at IWA, Phoenix Gateway Tower.

I think we need an ASE question asking what is the significance to pilots if a tower is a Contract tower.  If it hasn't already been covered--

Does this answer your question? Can an airport without an FAA controlled tower have their own tower and controllers?

The document linked in the as-duplicate thread lists airports that are FCT & NFCT, including IWN (an FCT). Voting to close as duplicate.

@757toga I think I'll respectfully disagree (except re IWN - that was a typo in my comment). This question asks "how can I tell..." and the answer in the linked question provides links to documents with lists. And the list there includes IWA and matches the info shown below. If the linked documents are out of date, best to fix that in one place (that question) rather than have separate questions linking to differently-dated documents.


text:
How to convert European ATC license (and medical) to FAA equivalents?
I have an Air Traffic Controller license issued by the European union (compliant with ICAO standards).
Ratings for tower and approach radar with current validations for both.
How can I convert this to the FAA equivalent?
Together with that license I have a current European union Class 3 medical certificate, How can I convert this to the FAA equivalent (FAA class 2 medical I believe that would be?)

I am unaware of any conversion process. You would have to find an employer or school to sponsor your taking the Control Tower Operator exam, and get an over-the-shoulder checkout on live traffic, in order to work Local Control at a facility in the US. The radar ratings would similarly require training and a checkout at a specific radar facility.

And you will likely not be able to "convert" a medical certificate. I suggest you schedule a consultation with an FAA designated AME. You will likely have to go through the FAA medical certificate process.

To work as an FAA controller you must be a US citizen.
Certifications are not transferable. You would have to be hired by the FAA and go through the FAA academy in OKC. If you pass OKC, you would then have to go to your assigned facility and pass their training program.
Past ATC experience is not a predictor of success. In our facility, people with prior experience took longer to train and had a higher washout rate than those hired with no ATC experience.

ATC qualifications and medicals are not transferable between juristiction areas. Each area will require you to regain these qualifications.
In regards to the medical, these are renewed regularly so it should be no major issue or inconvenience.
The ATC licence is different where you will most likely have to do training and assessment, though the training can be shorten due to recogniton of prior knowledge.
Also some countries have citzenship requirements I am not sure if USA does, but see this question (Can non-FAA towers employ foreigners?) for some more information.

FAA controllers must be US citizens.


text:
How does altitude affect sound?
So I know that altitude affects the speed of sound because of temperature differentials in the atmosphere, but I am curious what else affects how we hear planes overhead?
When a plane flies overhead, you dont hear a very constant filter at all frequency bands. It seems that lower frequencies are more consistent, where high frequencies seems to fade in and out, sounding much like a low pass filter.
Is this the product of the temperature differentials between you and the plane changing as the plane moves, or are there other factors? Does moving air affect the sound in any way?

I'm voting to close this question as off-topic because it's not about aviation, but about physics.

@Federico Hmm... the "or are there other factors" may involve aviation, but specifically how altitude affects sound is more of a pure physics question. I'm not completely certain this is off-topic, but it does seem likely that it could get a better answer at [physics.se].

I'm not sure if this is so off-topic for aviation, Sound and its effects are very important for aviation. For example, I studied Aerospace Engineering, and I had several classes on sound generation, sound propagation, and noise mitigation.

The answer to your question has a lot to do with how waves generated by a moving object propagate. You can see a full explanation here but the short answer is the Doppler Effect which causes pitch to change as the object moves buy you.
Here is a nice explanation
Edit:
My knowledge is a bit rusty but basically you are talking about a mechanical wave propagating through a fluid (the atmosphere) which will absorb some of the energy (eventually all of it). I would also thing that as the speed of sound changes the frequency of the wave would change much like the changes light has when it crosses different mediums.

hahah, that is an excellent clip :D I should have specified a bit more. I am also aware of the doppler effect. I am more curious about the filters and sound reflection within the atmosphere that produce the sense of distance for planes. I believe it is a combination of things, but I am not certain. I am attempting to build a DSP simulation of an airplane different altitudes


text:
What things do you consider when choosing a fixed base operator (FBO)?
I'm working on some marketing for a regional FBO and while I'm an aviation aficionado, I'm neither a pilot or deeply involved in the aviation industry.
I'd love your input on how you research and choose an FBO while doing your flight planning…

As a pilot what are your primary considerations when choosing an FBO? Fuel cost, amenities, local knowledge, other things entirely?
What things do you look at as distinguishing factors between competitors?
Are there certain things that you consider mandatory from an FBO?
What information do you want to "know before you go"?
What online resources do you personally use when doing your flight planning and/or researching FBO's?
Have you had an extremely positive (or terrible) experience with an FBO, so that I can research them?

I'll also note that this particular FBO is located in a fairly rural, yet growing region of the Western United States.
Look forward to your input and responses!

This seems mostly based on opinion, so it's not a good fit for the format here. If someone can address these topics well it may make a good post for the blog. If you can edit it to make it more based on facts, maybe surveys or sales data, it would be a better fit here.

This is an interesting question but it's a difficult one to answer here. You're asking for multiple opinions, but the purpose of this site is to find the best possible answer to reasonably factual questions. That's not to say that opinions aren't valuable, it's just that StackExchange isn't really about them. You might want to drop into the chat room and see what people think, or perhaps you can make your question more focused and objective (I know that may not be useful in this case).

I'll throw in my 2 cents here but I am by no means super experienced in this realm.

Amenities is not a huge deal for me. Generally I fly to go somewhere, while a nice interior is always a bonus, I'm fine as long as there is a bathroom and a receptionist to pay. Generally I'm at the airport to tie up and then leave and go about my business. Some place to sit to wait for weather to improve is nice but I by no means care if the couch is leather or 1970's velour as long as I can sit on it for a while.
I flight plan with ForeFlight.com so I won't comment on what you should have but in today's day and age I would consider a WiFi connection in the FBO a must have since lots of people use tablet based planning now.
Fuel cost is always a consideration and you should try and remain competitive to your local areas as much as possible.
The key for me is a well laid out and clear website that lists prices for what ever you offer and other important information. Maybe an airport map with the location of the FBO clearly marked. A phone number to call for questions is also important.
A solid relationship with a local taxi service is a bonus and a courtesy or rental car would be even better, but I understand how this could be a runaway cost on some level.
Local knowledge is good if there are specific things that may be odd about the airspace and major airport issues that may arise.

+1 for the WiFi... and not just any lame wifi:  An FBO that has big bandwidth and strong enough signal that I can download updated maps from the Ramp area is a really nice thing.


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Are there any regulations, standards or guidelines covering checklist typesetting, content, etc.?
I hope this question is on-topic for the site via ‘aviation safety’, as several aspects of checklist design are important as the actual content of the checklist e.g. ability to quickly hone in on the relevant section.
Although I mention regulations, this question does not refer to any specific jurisdiction.
Are there any regulations, standards or widely adopted guidelines that cover checklist production in the aviation industry? Or is it the case, that each manufacturer / supplier / airline is free to produce their own, with their own unique style?
Any links to any publicly accessible regs \ standards or guidelines would also be of interest.
I’m also interested in how the checklists are typically typeset, if known. I assume that it’ll be via standard software like MS Work or LaTeX, but it’s possible that there’s some really niche software vendors in this area.


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What kind of problems can a flight have if passenger weight is miscalculated?
There was a widely reported news story about a TUI Boeing 737 flight, where a bug in reservations system caused 38 passenger on the flight to be allocated a 38kg standard weight as opposed to the correct figure of 69kg. In total, this caused the report to state that the weight of passengers was 1200kg lighter than it actually was.
My question is - how serious of a problem is that? Would the pilot notice this discrepancies? What kind of problems could appear due to pilots using the wrong passenger weight in calculations and flight configuration?

Welcome to aviation.SE! We have a few questions already that might help you or even answer your question: here, here, here.

I don't know if this is a good answer, but 1200kg is about 3% of the weight of an empty 737.  I don't think they normally fill their fuel tanks, but take into account the actual weight which can vary from 41,000kg to 70,000kg depending on load.  I think they load extra fuel plus a 5% reserve for the flight, but if there are delays in landing and the flight is thought to weigh less than it does that might contribute to a fuel shortage.

In general, an incorrect takeoff weight can have serious consequences for an airliner, especially when the actual TOW is close to the RTOW (regulated takeoff weight, see e.g. this question: What is RTOW and how is it different from MTOW?). It is possible that the aircraft is unable to takeoff within the available runway length. This is particularly important in case of an engine failure during the takeoff, since normal performance with both engines operating typically has enough margins. Even on a long runway, the pilots might rotate too early because of an incorrect rotation speed (VR), which could result in a tail strike.
In this particular case, the difference in performance was minimal. The AAIB (Air Accidents Investigation Branch of the UK) investigated the incident and concluded:

Whilst an incorrect takeoff weight was used for aircraft performance planning, the thrust
required for the actual TOW and environmental conditions (88.2% N1
) was marginally less
than the thrust used for the takeoff (88.3% N1
). This meant the safe operation of the aircraft
was not compromised.

The report also shows the difference in the performance calculations with the incorrect (left) and correct (right) TOW:

The difference in the V speeds for takeoff is just one knot, which is not significant enough to have any adverse impact on the takeoff.

Begs a whole new question: "Are pilots, in general, precise enough to rotate at 139Kt vs 140Kt?" I do notice that on the left (incorrect) screen, it indicates SEL TEMP 44°C and on the right (correct) screen they have SEL TEMP 42°C. I'd think that would probably make a notable difference, too, would it not?

@FreeMan The difference between 139 and 140kt is less than a second, so it makes no difference for the rotation. The rotation rate is more important than that. The SEL TEMP is the assumed temperature for the thrust reduction. The difference here is what causes the difference in takeoff N1 (88.3% vs. 88.9%) below D-TO-2.

+1 Nice to get a grounded non sensational answer.

Did you mean 88.3% vs 88.9%?

@user2705196 88.3% was the thrust used (calculated with wrong TOW), 88.9% is what the calculations with real TOW would have given and 88.2% was the legal minimum with real TOW and actual environmental conditions.

Ah. Thanks. I got confused with the highlighted numbers and the quote!

For "what kinds of problems can appear", there's the case of Air Midwest Flight 5481, which crashed on takeoff partly due to a miscalculation of passenger weight.  In addition to needing additional power to accelerate the additional mass, the distribution of passenger weight can also affect where the center of gravity of the plane is. If the center of gravity of the plane moves too far relative to the center of lift, this can have dire consequences for the stability of the aircraft.

The investigators determined the crash to have been the result of the combination of two separate issues.
...
[First,] investigation revealed that turnbuckles controlling tension on the cables to the elevators had been set incorrectly, resulting in insufficient elevator travel, leading to the pilots not having sufficient pitch control.
...
Although the pilots had totaled up the take-off weight of the aircraft before the flight and determined it to be within limits, the plane was actually overloaded and out of balance due to the use of incorrect Federal Aviation Administration (FAA)-approved passenger weight estimates. When checked, the National Transportation Safety Board found that the actual weight of an average passenger was more than 20 pounds (9 kg) greater than estimated. After checking the actual weight of baggage retrieved from the crash site and passengers (based on information from next-of-kin and the medical examiner), it was found that the aircraft was actually 580 pounds (264 kg) above its maximum allowable take-off weight with its center of gravity 5% to the rear of the allowable limit.
It was determined that neither problem alone would have caused the loss of control, which explains why it had previously been flown without incident and had safely departed Huntington, West Virginia.

This said, note that the plane in this incident was a 19-passenger Beechcraft 1900D instead of the Boeing 737 in the recent incident.  Smaller planes are much more sensitive to weight distribution issues.

Stories like these are why I asked the question - most of them are about smaller planes and I was more specifically interested in bigger planes and airliners.

The crew would not notice a 1200 kg overload on an airplane the size of a 737.  The weight error will likely be randomly distributed with little C of G impact, and for an overload to be noticeable, there would have to be a significant change in performance at rotation that surprises the crew.  This will show up as an unexpected lag in lift off following rotation, and you won't get a noticeable lag with a load that only adds one knot to V speeds.
Depending on the humidity they have to deal with and whether or not there are dehumidification systems (called zonal dryer systems) to keep the air at the outer skin dry, these airplanes often unknowingly fly around with 100s of pounds of water ballast from condensation that has soaked into the insulation, that generally goes un-noticed (no detectable performance hit) until the airplane goes in for C check where the interior panels come out.

Before take-off, pilots enter a number of figures into the flight computers. Among them, they enter:

The total weight of the plane
Adjusted thrust

No sense using full thrust on a lightly loaded plane (which would get you a very short take-off) when you could reduce thrust a bit even if that means using a longer part of the runway.
As has been shown in the case of Emirates Flight 407, a single error can then lead to nearly-catastrophic consequences. Incorrect data were entered in the Electronic Flight Bag*, and the takeoff parameters were then entered into the flight computer. As the plane was a lot heavier than the figure entered, the thrust wasn't enough to get the aircraft off the ground before the end of the runway (actually 148 m beyond that!), and hit quite a few things while very slowly gaining altitude after that.
* In this case it was the "Airbus Less Paper Cockpit (LPC) system. The LPC system replaced the majority of the aircraft's operating documentation with a laptop computer-based system." (preliminary investigation PDF)
Now, the error there was massive: 262.9 tonnes instead of 362.9, a full 100 tonnes!
A similar incident happened with AF 6724, with input of 243 tonnes instead of 343. Again a full 100 tonnes!
The error in the case of the TUI flight was 1200 kg (1.2 tonnes). As explained in the report, this resulted in a very minor difference in all parameters. Note that a 737 is much lighter than the 340-500 or the 777 in the examples above (take-off weight was around 65 tonnes), so it's not 100 times less in proportion, but it's still significantly less.
However most aircraft incidents are not due to a single error, but an accumulation of errors large and small that finally end up tipping things over, as every single error removes a bit of a safety margin.
In this case, the report tell us that as a result of the error, thrust was set to 88.3% N1 instead of 88.9% N1. It was still slightly above the minimum for safe take off (88.2% N1), but as you can see, safety margins have been significantly reduced!
Note that in any case passenger weight estimates are just that, estimates. They're also often a relatively minor part of the total weight when compared to the aircraft itself and fuel. But they're still important enough that they need to be carefully considered, and have been readjusted over time to reflect changing patterns.

Oh, I didn't know about the Emirates Flight 407. That really puts it into perspective.

Takeoff performance calculations include not only weight, but balance.  Part of the output from takeoff calculations include airspeeds (which are based on weight, temperature, runway conditions, runway selection, runway length, wind, and other factors such as reduced power selection, flap use, etc.  Takeoff calculations also include the pitch trim setting to be used, and this is impacted by factors such as the flap setting and primarily the aircraft balance.  Takeoff pitch trim is a value which will change in flight, but is an initial setting affecting controllability and the control forces needed to pitch to and maintain a takeoff attitude.
An excessive aft center of gravity with the wrong pitch trim setting might make it easier to over-rotate, causing a tail strike, or a forward center of gravity, to under rotate, prolonging the takeoff roll.
Airspeed calculations are more than just reaching a minimum speed, but take into account minimum controllable speeds on the ground and in flight, minimum speed to fly, maximum speed to reject the takeoff and be able to stop the aircraft, and the takeoff safety speed for all engine climb, and for loss of an engine after takeoff.   If the speeds have been calculated based on incorrect values, then also affected are the flap setting, which may be wrong for the weight or runway or conditions.
Incorrect balance is more noticeable than incorrect weight, up to a point.
1200 kg may not be an excessive value if well under maximum weight for the conditions, and ample runway exists and if the temperature isn't excessive, and surface conditions (such as icing) don't further restrict weight for a rejected takeoff, etc.  It may be a significant issue depending on where that weight causes the center of gravity to fall, especially if the aircraft was already near one end of the operating envelope.

While in absolute terms, a miscalculation of TOW is going to affect a smaller aircraft more significantly, here's an example of a 'near miss' on an A340: the pilots were lucky to keep the thing aloft after the F/O entered a digit incorrectly into the aircraft's weight parameters (used for thrust settings at takeoff in conjunction with runway length). Airbus revised its weight and balance thrust calculator after this incident, and the pilots returned to DXB and resigned on the spot, it's a good example of how it can all go wrong: https://www.atsb.gov.au/media/3531728/ao2009012_full%20report.pdf

By my calculations, entering the first digit of the total weight incorrectly will have a FAR FAR worst effect than even the worst possible passenger weight miscalculation. 400 passengers at 80 kilos each is "only" 32 tons.

For one example, read the report in one ASRS Callback issue under the heading, "The Bod Squad". It's about a B727 carrying a football team. Long takeoff roll, poor climb, and inability to reach planned altitude are some of the problems mentioned. Fortunately, the flight was completed without any mishap. But the potential for an accident was certainly there.

Unlike the case here, the real problem was not the miscalculation but the fact that the B727 was hugely above its maximum weight, estimated 8,000 pounds. In this case the weight was just 1,200 pound above the estimate, and well within the normal range.

@gnasher729: The overweight condition was because normal average weights were used, but the passengers were well above normal average weights.


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What is this INOP instrument and when is it safe to fly with INOP instruments?
I flew ZRH->LHR on BA0711 today on G-EUOG. I noticed through the cabin door one of the instruments had a yellow INOP sticker across it (see photo). Which instrument was it? I am presuming the instrument has a backup, and the backup was operative, but I had thought the purpose of an backup was so that it could be used if the primary failed in flight? Or is the instrument just 'not important'? What are the rules re flying with INOP instruments?

I'm not sure what instrument it is, but the ironic part is that the sticker makes it legal to fly with the INOP instrument. Without the sticker it would be against the rules (at least in the US). This includes instruments that go INOP in flight, which is why some aircraft have sticky notes or INOP stickers on board.

In case it helps someone, G-EUOG seems to be an Airbus A319-131.

@RonBeyer it's quite possible for something to ground the aircraft when INOP, would still be marked just as a reference for maintenance and a warning to other crew to not fly the aircraft.

@RonBeyer Well, it's not as stupid as it sounds.  A big INOP sticker makes it obvious that the instrument is not functioning.  Without a sticker what is to stop a pilot from forgetting that the intstrument is broken and then reacting inappropriately to the (incorrect) information displayed?

@jwenting I don't think I suggested that it wasn't the case, I've grounded aircraft myself because of INOP equipment, and made sure it was marked properly for the maintenance people.

@J... I didn't say it was stupid to mark it out in flight, or mean to suggest that. The "ironic" part for me is that if you are flying and an instrument goes INOP, you may be in violation of a FAR unless you mark it out, but who is going to verify that?

@RonBeyer Well, it's like anything else.  It's in the pilots' best interest to mark it out because, first and foremost, it's they who will end up making mistakes with it.  In most cases maybe nobody would notice but I imagine it's not the kind of thing you want to let slide and have come out in an NTSB investigation when something does go wrong.  You could say the same thing about skipping checklists - who is going to verify that they were done?  If nothing goes wrong, maybe nobody... I don't think it's ironic that people should follow checklists, though.

It is a standby display, specifically a DDRMI (Digital Distance Radio Magnetic Indicator).
The aircraft can be dispatched with inoperative equipment. The process is controlled by a Minimum Equipment List (MEL). The operator will have an MEL for each type of aircraft in their fleet. The MEL is approved by the regulatory authority (FAA, CAA, etc.) and specifies what may be inop and associated restrictions.
I don't know what the BA MEL for the A319 is, but here's a snip from the FAA's Master MEL (MMEL), which is the guidance for each operator to use when creating their MEL.

Following this guidance, the MEL would say you can dispatch with the DDRMI INOP if the FAR equipment minimums are met. That (at least in the US) is along the lines of "navigational equipment necessary for the planned flight".

I am presuming the instrument has a backup, and the backup was
  operative

The "INOP" instrument itself is a backup. It is a navigation instrument which combines a compass, VOR needles and ADF needles. This backup instrument is an analog version which runs on 70s tech. It is rarely (if ever) needed, only intending to be used when all cockpit computers fail, which is exceptionally rare. The modern version uses computers and the results are displayed on the screens you see.

What are the rules re flying with INOP instruments?

As others have stated, the "Minimum Equipment List" is a document that lists what equipment is essential for an aircraft to be dispatched.
Besides safety, dispatch rate is another reason why there is redundancy in an airliner cockpit. With systems as complex as this (the manual of a modern airliner is thousands of pages long), failures are not unusual. It is more economical to design an aircraft that can still fly with some instruments / systems inoperative rather one which requires everything to be 100% working.

The instrument is a backup VOR gauge. It's there in case manual radio navigation is needed (hardly in a modern airliner) AND the displays are not working.
As it's not an instrument that's vital for getting the aircraft on the ground safely, it's no problem if it's declared INOP (there is probably a maximum time period for it to be marked as such before repairs are required).

Every aircraft has a MMEL (Master Minimum Equipment List) and a MEL (Minimum Equipment List).
While the MMELs are published by the producer of the aircraft, MELs are generated by the companies flying these airplanes. Every company may have different MEL for the same aircraft. This MELs cannot be shorter than the MMEL.
If that malfunctioning or inoperative equipment is in the MEL that aircraft cannot fly without special permissions.
This is the basic information. For more information you can read Wikipedia or FAA, JAR or EU OPS publications.


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What would happen if a helicopters rotor hit the [in-air] refueling probe?
My first guess is that they would catastrophically fail - but I also read the Eurocopter Cougar has propeller blades that will withstand the impact of a 20mm round (I'm guessing other military helicopters are similar).
Is it likely that the probe could bounce off or is it a pretty much guaranteed byebye scenario?
Also could the rotor become entangled in the hose or would it simply slice it?

It would chop it right off.
Watch the video. It's fun. When the helicopter pitches up right after refueling, the rotor disc cannot follow the movement (its hinges allow the blades to pitch up and down, and inertia makes it change its plane of rotation only slowly). The refueling probe is cut cleanly in half.
However, I would not try this on purpose. The risk of damaging a blade is considerable. I am sure the rotor blades needed to be replaced after that incident.

I'll keep it in mind if for the extremely unlikely scenario that I would ever have to refuel a helicopter in mid air. DONT CRASH DONT DIE OHNO DONT HIT THE PROBE. Thanks.

It is not because of the rotor inertia. It is because the rotor pitch controls the helicopter pitch. The helicopter pitched up so to get its nose down the rotor needed to pitch down and that is what the pilot did did.

Apparently it snips the probe off. No report of wether the rotor was damaged, the probe may have been built with this in mind, and thus out of weaker materials than the rotor blades.
https://www.youtube.com/watch?v=VAdpKpppZiA

I don't know, but if it was me, I'd much rather have what essentially amounts to a hose cut off, than the rotor blades. And design both accordingly. With plenty of margin for error.


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What's the preferred approach for a passenger jet?
I seemingly can't find an answer to this quite obvious question:
What's the preferred approach procedure for a passenger jet at a modern airport fully equipped for precision ILS (both aircraft and airport): ILS or visual approach?
If it's ILS, what would cause a visual approach to be flown (except for the ILS not working of course)?
If it's visual,

a. why? (ILS seems more secure from my naive standpoint)
b. what would be the cause to do ILS instead? Bad weather / sight for instance?

Is the decision made only by the tower or does the captain of the aircraft have any saying in it?

Absolutely not a duplicate question.  Plenty of aircraft CAN NOT autoland, but there is still the choice between a visual approach or an ILS approach.  Not the same question, and the answers won't be the same here as for that question.

Note, that flying visual approach does not mean ILS is not used. It just means visual contact is required. Most pilots will still use ILS for cross-check if it is available.

I'll give the answer from an ATC perspective. A visual approach is the most preferred approach, since we can get aircraft to follow each other, and don't have to worry as greatly about aircraft getting too close. The rules say we can compress under certain conditions to 2.5 miles on ILS or radar separation approaches, but timing wise, for the runway to be clear, you can often need less separation between aircraft to maximize its usage. With the visual approach, you're vectoring to keep aircraft closer so they can see each other and follow in closely to each other to the runway.
In most ATC facilities, the Tower decides what runway to use, and the approach control calls the type of approach generally on offer(this can vary depending on facilities and how they agree to run things). A pilot can always request a different approach... they might be delayed, sometimes significantly if they insist on something way out of the loop.

That's an interesting addition on the answers given in the duplicate that I missed, thank you very much!

Given the caveat that I retired in 1999 and cannot speak for today's pilots, my thinking and the observed preferences of the great majority of the pilots I flew with follow.
With few exceptions, a visual approach was preferred over an ILS for the simple reason that it's usually quicker, and over time in large aircraft, the fuel savings can be significant for your company. I did know a few pilots, though, that liked to stay in the air longer to increase the size of their paycheck when being paid by the flight hour. I always felt this was unprofessional. A 747-100/200 (my airplane for my final 10 years) burns a lot of fuel, and part of the captain's responsibility is not costing the company money if you don't have to. Also, if you have people in the back making connections, you want to maximize the time they'll have to make those connections.
There are times, though, even with CAVU conditions, you may want the ILS. For example, I was offered the visual approach one night into Hunter Army Airfield in Savannah, Georgia. It was my first time there, and locating the runway in the maze of lights made it unwise to accept. In fact, I found that airfield so hard to find visually at night, that I continued asking for the ILS until I had been there several times.
Of course, if it's clear, but you're going into LAX on a hundred mile final from the east with 15 or more aircraft doing the same, you don't even think about a visual.
Generally I followed the practice of requesting a visual approach when first possible going into familiar airports when the traffic was light and there was time to be saved.
There were pilots of foreign airlines that would never request a visual. For example, Japan Air and Korean Air going into Anchorage in the early 1990s always requested an ILS. If it wasn't available, they would request a VOR approach. As I understand it, their training, culture, and experience (as explained to me by a JAL check captain) didn't favor being able to just look at a runway and land.
It's a minor point, but to me visual approaches offered more opportunities to play.

I also preferred the visual.  I made a habit of calling out visual contact with the airplane in front of me ("Newark tower, jetlink 1234 with the 737 traffic over TEB in sight"), which usually got me the visual clearance.  I'm also sure the guys at the EWR tower were happy to be relieved of spacing concerns (particularly when they'd squeeze us onto 11 in between the 22L/4R arrivals).

even on the visual, many large airports with straight in approaches (eg, NOT JFK), will tell the pilot, "turn left 020, intercept the localizer, descend and maintain 3,000". so even though you're officially on the visual, you're still tracking the localizer.
Other airports have published visuals with waypoints, like SFO Quiet Bridge  https://www.globalair.com/dtpp/globalair_00375QUIETBRIDGE_VIS28LR.PDF

What makes a visual approach quicker than an ILS approach? As a non-pilot, I can't see why there would be any difference, speed wise?

@GavinCoates The first sentence of your comment would make a good regular question and thus allow for a full answer. A short answer is that there are a number of things. Perhaps easiest to understand is the situation where you are, say, coming in from the south and the runway in use is landing to the south. If you fly an ILS approach, you're going to be taken to a point at least 5 miles north of the airport before turning back. If you're on a visual, you need to get only as far north of the airport to allow a turn back. One mile would be sufficient. Ask as a question and I'll give more detail.

@Terry done: http://aviation.stackexchange.com/questions/24275/what-makes-a-visual-approach-quicker-than-an-ils-approach


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FAR 91.411 and 91.413 pitot/static and transponder tests when overseas
I own an N-registered aircraft and am overseas with it. The aircraft requires compliance with FAR 91.411 and FAR 91.413. In looking at the FAA database for repair stations, I don't see a station authorized to perform these tests in this country. I'm a bit stumped, how can I comply with these regulations?

In what country?

Do the US regulations apply when flying in foreign airspace?

@mins Most of them do, yes, under 14 CFR § 91.703, unless preempted by local or ICAO regulations.

To the points above: they do for the aircraft. There are reciprocal arrangements. My question is how to get the required FAA paperwork to comply with them?

You don't need to find a full FAA-certified repair station. Anyone with a US airframe mechanic rating and access to the proper equipment with current calibrations can do that for you. Pitot-static and transponder test equipment is a fairly common thing to find, especially if you are US certified and offering your services overseas.
AC-43-6D states...

MAINTENANCE. Any appropriately rated person (as specified in § 43.3) may perform maintenance or preventive maintenance on an aircraft altitude reporting and transponder system. This work may include the removal of and/or replacement with an identical system component. An appropriately rated person can approve the aircraft for return to service only after the performance of a suitable functional check of the entire system (as installed in the aircraft) to determine that the system, as well as the component, will perform its intended functions.

Yes. In the end that’s what I found out.